ALBANY — The number of students opting out of New York's Common Core-based exams appears to be approaching 2015 levels, fueled in part by a boost on Long Island.

An unofficial count by United to Counter the Core found parents opted out at least 175,000 students from the state's English language arts exam, which was administered to grades three through eight last week.

Wednesday marked the first day of the state's math exam. Testing continues Thursday and Friday.

The survey by the Long Island-based group that helped organize the testing protest is based largely on media reports and numbers collected by opt-out groups. The state will release official figures later this year.

It includes figures from about 53 percent of the state's roughly 700 school districts, finding about 15 percent of students in those districts refused the English test. Like last year, a higher number of parents are expected to opt their children out of the math exam.

"It's not about the number," said Lisa Rudley, an Ossining parent and co-founder of NYS Allies for Public Education, a group that helped organize the protest. "It's about there being enough people out there who are still outraged, who are still not having their kids take the test. It's still a problem."

The testing boycott, which is now in its third year, is rooted largely in parent-led groups who have criticized the state's reliance on testing, particularly after the roll-out of the Common Core education standards in recent years.

The state Education Department, meanwhile, has made changes to the tests that officials had hoped would alleviate parental concerns, including an eased time limit for students and tweaks made to slightly shorten the tests.

High Achievement New York, a business-backed group that has aired radio advertisements encouraging parents to allow their children to take the exams, have said the available opt-out data suggest test refusals have held steady.

"In fact, the tide on opt-outs appears to have been stemmed, with overall participation rates flat across the vast majority of the state," the group wrote in a memo released to the press. "More parents have opted their children in to assessments in regions throughout the state, with the exception of Long Island."

Robert Lowry, deputy director of the state Council of School Superintendents, said the general sense is opt-outs have increased on Long Island, while districts in the rest of the state have seen mixed results.

He said most superintendents have reacted positively to the shift to untimed testing, which many opt-out organizers opposed.

"That's something we supported while acknowledging the concern over the vision of a child struggling for hours," Lowry said. "But the general sense is it provides a fairer test of students actual performance."

On Monday, NYS Allies for Public Education issued a news release claiming the untimed tests could run contrary to a 2014 state law limiting how much instruction time can be spent on testing.